As a means for obtaining color separation images Y (Yellow), M (Magenta), C (Cyan) and K (Black) necessary for color printing, an image reproducing system such as a color scanner is used. Recently a so-called layout color scanner (system) has been put to practical use in some fields. The function of such a system is to record plural images, including letter components, as well as to perform layout operations such as magnification conversion and positioning.
This kind of color scanner system, having functions of performing layout and image correction, obtains color component data B (Blue), G (Green) and R (Red) by scanning an original picture, performing color and gradation correction and magnification conversion on the color component data B, G and R, and converting the processed data B, G, and R into color separation data Y, M, C and K to produce color separation images Y, M, C and K. In this process, said color separation data Y, M, C and K are stored into a large capacity input memory such as a disc memory and are used as data for layout operations or image correction by being read directly from the large capacity input memory or from a memory provided in the image reproducing system to which said data are transferred beforehand. Meanwhile, oridinarily a large volume of image data is involved. For example, if 100 M byte storage capacity is necessary for data of one color separation, a total of 400 M byte capacity is required for data of four color separations. In addition, because of an increase in output data volume required in performing layout operations on the scanner, the memory capacity must be still larger. Moreover, output said large capacity memory, which may be a disc memory, is so expensive that it may account for virtually the entire cost of the system, which also requires efficient use of the memory.
Thus, in order to permit a reduced memory capacity, the following method is proposed. The proposed method adopts steps of storing into an input memory B, G and R color component data obtained from an original picture using an input device such as a scanner, converting the color component data B, G and R read from the input memory into color separation data Y, M, C and K, performing layout operations such as assembly, color correction, and gradation correction on the color separation data Y, M, C and K, and storing the processed color separation data Y, M, C and K into an output memory.
However, the abovementioned method is still deficient in realizing a reduced memory capacity because the final data to be stored into the output memory are still four color separation data Y, M, C and K.
To resolve the above defect, the following method is proposed. This method adopts steps of storing color component data B, G and R obtained from an original picture into an input memory, performing no layout processing such as color gradation correction, or performing only assembling operations, on the color component data B, G and R, storing said color component data B, G and R into an output memory, and performing every kind of correction by using a calculator provided in the image reproducing system on the color component data B, G and R when they are read for use for recording an image.
However, originally a layout scanner must function to perform layout operations such as assembling or correction for images situated inside of line frames on four color separation data Y, M, C and K. Moreover screen tint generation or flat tone generation (wherein specified areas are expressed by the halftone in specified density and in specified color with an optional one or more of four color separation images Y, M, C and K) must be performed, and lines (including wide lines such as thick frames) and drawings, such as letters of designated colors, must be expressed in one of the separation colors.
But the latter method can only afford to manage three color component data B, G and R in the layout process and cannot produce a black image with one color component data, so it has not been put into practice. Precisely, when a ruled line is desired to be recorded with pure black in (K=100%), naturally Y, M and C color inks are not needed for recording the ruled line (Y=M=C=0%). While to express pure black, the color component data B, G and R must be ful density--(B=G=R=100%) which results in a calculation of the color separation data Y, M and C, when the color component data B, G and R are fixed in the above condition, to be a full density (Y=M=C=100%). Such a result makes the ruled line turbid and prevents it from being recorded with pure black.